Preparation method of water-soluble PEDOT-S and application of water-soluble PEDOT converted into water-insoluble PEDOT in solid-state capacitor

Abstract

The invention discloses a preparation method of water-soluble PEDOT-S and application of water-soluble PEDOT converted into water-insoluble PEDOT in a solid-state capacitor, and belongs to the technical field of capacitors. The method comprises the following steps: providing a water-soluble EDOT monomer; the preparation method comprises the following steps: dissolving a water-soluble EDOT monomer in deionized water, adding a catalyst, and uniformly stirring to obtain a mixed solution; under a nitrogen protection environment, dropwise adding an oxidant solution into the mixed solution for reaction to obtain an intermediate product after the reaction is completed; performing dialysis membrane or ion exchange resin treatment on the intermediate product, and removing low-molecular-weight by-products to obtain a water-soluble PEDOT-S solution. The method has the beneficial effects that the water-soluble PEDOT-S cathode is converted into the non-water-soluble PEDOT cathode through drying at a certain temperature, and by utilizing the temperature control conversion mechanism, the capacitor can keep stable capacitance performance in application, and meanwhile, the problem of water absorption of the capacitor in the long-term storage process is avoided.

Description

Technical Field

[0001] The present invention relates to the technical field of capacitors, and in particular to a method for preparing water-soluble PEDOT-S and converting it into water-soluble PEDOT for application in solid-state capacitors. Background Art

[0002] Conductive polymers have been widely used in the field of electronic components due to their excellent conductivity and electrochemical stability, especially in solid-state capacitors, where they are often used as anode or cathode materials. Traditional poly (3,4-ethylenedioxythiophene): polystyrene sulfonate) (PEDOT:PSS) dispersions occupy an important position in solid-state capacitor cathode materials due to their high conductivity and flexibility. However, PEDOT:PSS has exposed many technical defects in practical applications. The particle size of its dispersion is large, and high-pressure homogenization is usually required to obtain a uniform dispersion effect. However, high-pressure homogenization not only has high requirements for equipment, increases manufacturing costs, but also limits the large-scale industrial application of materials. In addition, PEDOT:PSS dispersions are prone to stratification during long-term storage, and the conductivity decays significantly over time, resulting in poor storage stability, affecting the reliability and service life of the final product. Its high viscosity characteristics further limit its applicability in fine coating processes, which can easily lead to uneven coatings, thereby negatively affecting the performance of solid-state capacitors.

[0003] In response to the above problems, water-soluble self-doped conductive polymer PEDOT-S (sulfonated poly 3,4-ethylenedioxythiophene) provides a solution. However, the performance of capacitors prepared using water-soluble PEDOT-S as the cathode is unstable and there is a problem of water absorption during long-term storage, which seriously affects the performance of the capacitor. Therefore, the problem of water absorption of capacitors has become a technical problem that needs to be solved urgently in the application of water-soluble PEDOT-S in capacitors. Summary of the invention

[0004] The purpose of the present invention is to provide a method for preparing water-soluble PEDOT-S and converting it into water-insoluble PEDOT for use in solid-state capacitors. By introducing self-doping functional groups (such as sulfonic acid groups) into the molecular structure, PEDOT-S achieves a self-dispersion effect without the need to add additional exogenous dopants; its optimized aqueous phase polymerization process can directly prepare a conductive polymer solution with a small particle size and uniform distribution, without the need for high-pressure homogenization treatment, greatly reducing the preparation cost and equipment complexity; at the same time, by converting water-soluble PEDOT-S into water-insoluble PEDOT through a temperature control method, not only can the stability of the capacitor be improved, but also the problem of water absorption of the capacitor during long-term storage can be solved, thereby solving at least one technical problem involved in the background technology.

[0005] In order to solve the above-mentioned technical problems, the present invention is achieved as follows:

[0006] The present invention provides a method for preparing water-soluble PEDOT-S, comprising the following steps:

[0007] Step S1, providing a water-soluble EDOT monomer;

[0008] Step S2, dissolving the water-soluble EDOT monomer in deionized water, adding a catalyst, and stirring evenly to obtain a mixed solution;

[0009] Step S3, under a nitrogen protection environment, adding an oxidant solution dropwise to the mixed solution for reaction, and obtaining an intermediate product after the reaction is completed;

[0010] Step S4, treating the intermediate product with a dialysis membrane or an ion exchange resin to remove low molecular weight byproducts, thereby obtaining a water-soluble PEDOT-S solution with high dispersibility and low viscosity.

[0011] Optionally, in step S1, the preparation method of the water-soluble EDOT monomer is as follows:

[0012] Hydroxymethyl EDOT is dissolved in an appropriate amount of deionized water, sodium hydride is added, and a sulfonic acid reagent or a carboxylation reagent is added dropwise after stirring at room temperature for a certain period of time, and then the temperature is raised to reflux for a certain period of time, and a water-soluble EDOT monomer containing a sulfonic acid group or a carboxyl group is obtained after purification.

[0013] Optionally, the molar ratio of hydroxymethyl EDOT to sodium hydride is 1:1.0-1.5.

[0014] Optionally, the reaction is stirred at room temperature for 4 hours, and the reaction is refluxed for 15 to 24 hours.

[0015] Optionally, in step S2, the molar ratio of the catalyst to the EDOT monomer is 0.2 to 1:1.

[0016] Optionally, in step S2, the catalyst is ferrous sulfate or ferric sulfate.

[0017] Optionally, in step S3, the molar ratio of the oxidant to the water-soluble EDOT monomer is 1 to 2:1.

[0018] Optionally, in step S3, the oxidant is sodium persulfate or ammonium persulfate.

[0019] Optionally, in step S3, the dropping time is no more than 30 minutes and the reaction temperature is 25°C.

[0020] The present invention uses the water-soluble PEDOT-S prepared by the preparation method in the preparation of water-insoluble PEDOT solid capacitors, including:

[0021] The capacitor is immersed in a water-soluble PEDOT-S solution to obtain a capacitor with a water-soluble PEDOT-S cathode after sufficient infiltration, and is dried at a temperature of 150 to 180° C. to convert the water-soluble PEDOT-S cathode into a water-insoluble PEDOT cathode to obtain a water-insoluble PEDOT solid capacitor.

[0022] The beneficial effects of the present invention are as follows:

[0023] 1. In the application of capacitors, high-pressure homogenization treatment is not required, which greatly simplifies the production process. The present invention optimizes the molecular design of the conductive polymer and improves the dispersibility of the material by using self-doping functional groups, so that the water-soluble conductive polymer can directly form a uniform solution in the aqueous phase system. The experimental results show that the prepared conductive polymer solution has a uniform particle size distribution (D50≤80nm) and low viscosity (≤8mPa·s), which is suitable for the impregnation process and avoids the high-pressure homogenization treatment that must be relied on in the preparation of traditional PEDOT:PSS dispersions. This process simplification effectively reduces equipment costs and energy consumption, while improving the industrial preparation efficiency of materials.

[0024] 2. The conductive polymer solution exhibits excellent stability during storage, which completely solves the problem of easy stratification during storage of PEDOT:PSS dispersion. The present invention introduces self-doping groups into the molecular structure, so that the conductive polymer dispersion always remains uniform and free of stratification during long-term storage, and no precipitation occurs. The experimental results show that the conductive polymer dispersion is stored at 60°C and 90% humidity for 30 days, and the conductivity retention rate exceeds 95%, which is significantly better than the defect of rapid performance decay of traditional PEDOT:PSS dispersion under the same conditions due to stratification.

[0025] 3. In capacitor applications, the performance can achieve functional expansion and diversification of application scenarios. The conductive polymer prepared by the present invention has excellent electrochemical performance and is better than traditional materials in high temperature and high humidity environments. This makes its application in solid-state capacitors more extensive, and also provides potential application possibilities for other electronic components such as sensors, electrolytic capacitors and flexible electronic devices, showing great potential for functional expansion and multi-scenario adaptation.

[0026] 4. The present invention converts the water-soluble conductive polymer (PEDOT-S) cathode into a water-insoluble PEDOT cathode, thereby maintaining stable capacitance performance and avoiding the problem of water absorption of the capacitor during long-term storage. BRIEF DESCRIPTION OF THE DRAWINGS

[0027] In order to more clearly illustrate the technical solutions in the embodiments of the present invention, the following briefly introduces the drawings required for describing the embodiments. Obviously, the drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative work, among which:

[0028] Figure 1 This is the XPS sulfur spectrum of the film dried at 120°C provided by the present invention;

[0029] Figure 2 This is the XPS sulfur spectrum of the film dried at 180°C provided by the present invention;

[0030] Figure 3 It is a side chain cleavage mechanism diagram provided by the present invention. DETAILED DESCRIPTION

[0031] The technical solutions in the present invention will be described clearly and completely below in combination with the present invention. Obviously, the described embodiments are part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0032] Example 1

[0033] A method for preparing water-soluble PEDOT-S provided in Example 1 comprises the following steps:

[0034] Step S1, providing a water-soluble EDOT monomer, wherein the preparation method of the water-soluble EDOT monomer is as follows:

[0035] Dissolve hydroxymethyl EDOT (3,4-ethylenedioxythiophene-2-methanol) in an appropriate amount of deionized water, add sodium hydride, the molar ratio of hydroxymethyl EDOT to sodium hydride is 1:1, and after stirring at room temperature for 4 hours, add sulfonic acid reagent or carboxylation reagent dropwise, then heat to reflux for 15 hours, and obtain a water-soluble EDOT monomer containing sulfonic acid group or carboxyl group after purification;

[0036] Step S2, dissolving the water-soluble EDOT monomer in deionized water, adding ferrous sulfate, wherein the molar ratio of ferrous sulfate to the water-soluble EDOT monomer is 0.2:1, and stirring evenly to obtain a mixed solution;

[0037] Step S3, under a nitrogen protection environment, adding sodium persulfate solution to the mixed solution for reaction, the molar ratio of water-soluble EDOT monomer to sodium persulfate is 1:1, the dropping time is 25 minutes, the reaction temperature is 25° C., and after the reaction is completed, an intermediate product is obtained;

[0038] Step S4, treating the intermediate product with a dialysis membrane or an ion exchange resin to remove low molecular weight byproducts, thereby obtaining a water-soluble PEDOT-S solution with high dispersibility and low viscosity.

[0039] Example 2

[0040] A method for preparing water-soluble PEDOT-S provided in Example 2 comprises the following steps:

[0041] Step S1, providing a water-soluble EDOT monomer, wherein the preparation method of the water-soluble EDOT monomer is as follows:

[0042] Dissolve hydroxymethyl EDOT (3,4-ethylenedioxythiophene-2-methanol) in an appropriate amount of deionized water, add sodium hydride, the molar ratio of hydroxymethyl EDOT to sodium hydride is 1:1.3, add sulfonic acid reagent or carboxylation reagent dropwise after stirring at room temperature for 4 hours, then heat to reflux for 20 hours, and obtain a water-soluble EDOT monomer containing sulfonic acid group or carboxyl group after purification;

[0043] Step S2, dissolving the water-soluble EDOT monomer in deionized water, adding ferric sulfate, wherein the molar ratio of ferrous sulfate to the water-soluble EDOT monomer is 0.7:1, to obtain a mixed solution;

[0044] Step S3, under a nitrogen protection environment, adding sodium persulfate solution dropwise to the mixed solution for reaction, wherein the molar ratio of sodium persulfate to water-soluble EDOT monomer is 1.5:1, the reaction temperature is 25° C., and an intermediate product is obtained after the reaction is completed;

[0045] Step S4, treating the intermediate product with a dialysis membrane or an ion exchange resin to remove low molecular weight byproducts, thereby obtaining a water-soluble PEDOT-S solution with high dispersibility and low viscosity.

[0046] Example 3

[0047] Example 3 provides a method for preparing water-soluble PEDOT-S, comprising the following steps:

[0048] Step S1, providing a water-soluble EDOT monomer, wherein the preparation method of the water-soluble EDOT monomer is as follows:

[0049] Dissolve hydroxymethyl EDOT (3,4-ethylenedioxythiophene-2-methanol) in an appropriate amount of deionized water, add sodium hydride, the molar ratio of hydroxymethyl EDOT to sodium hydride is 1:1.5, add sulfonic acid reagent or carboxylation reagent dropwise after stirring at room temperature for 4 hours, then heat to reflux for 24 hours, and obtain a water-soluble EDOT monomer containing sulfonic acid group or carboxyl group after purification;

[0050] Step S2, dissolving water-soluble EDOT monomer in deionized water, adding ferrous sulfate, wherein the molar ratio of the water-soluble EDOT monomer to the ferrous sulfate is 1:1, and stirring evenly to obtain a mixed solution;

[0051] Step S3, under a nitrogen protection environment, dropwise adding ammonium persulfate solution into the mixed solution for reaction, wherein the molar ratio of sodium persulfate to water-soluble EDOT monomer is 2:1, the dropping time is 29 minutes, the reaction temperature is 25° C., and after the reaction is completed, an intermediate product is obtained;

[0052] Step S4, treating the intermediate product with a dialysis membrane or an ion exchange resin to remove low molecular weight byproducts, thereby obtaining a water-soluble PEDOT-S solution with high dispersibility and low viscosity.

[0053] It should be noted that by modifying the molecular structure, a variety of hydrophilic functional groups (such as sulfonic acid, carboxyl, amine or polyether chains) are introduced. These functional groups enhance the water solubility and dispersibility of the monomers through the intramolecular self-doping effect, and achieve a balance between conductive properties and chemical stability.

[0054] In the process of synthesizing water-soluble PEDOT-S, sodium persulfate (Na2S2O8) is selected as an oxidant and iron salt (such as FeSO4) is used as a catalyst. By adjusting the molar ratio of the oxidant to the water-soluble EDOT monomer (1:1 to 2:1) and the molar ratio of the catalyst to the water-soluble EDOT monomer (0.2:1 to 0.6:1), precise control of the polymerization reaction rate and the structure of the product is achieved. In addition, changes in the reaction medium environment (such as vacuum environment, air environment, nitrogen environment, etc.) further optimize the polymerization efficiency and final conductive properties. After the polymer is prepared, the by-products are removed by ion exchange membranes or ion exchange resins, and finally a water-soluble PEDOT-S solution with uniform dispersion, small particle size and high stability is obtained.

[0055] The water-soluble PEDOT-S solution prepared by the method provided by the present invention exhibits excellent physical and chemical properties. The particle size distribution is uniform (D50≤80nm), the solution viscosity is low (≤8mPa·s), the conductivity is high (≥100S / cm), and there is no stratification or precipitation phenomenon during long-term storage, and the conductivity performance retention rate exceeds 95%. This water-soluble conductive polymer material is significantly superior to traditional PEDOT:PSS in conductivity, uniformity and storage stability.

[0056] Example 4

[0057] The present invention uses the water-soluble PEDOT-S prepared by the preparation method to convert into water-insoluble PEDOT in a solid capacitor, including:

[0058] The capacitor is immersed in a water-soluble PEDOT-S solution to obtain a capacitor with a water-soluble PEDOT-S cathode after sufficient infiltration. The capacitor is dried at a temperature of 150 to 180° C. to convert the water-soluble PEDOT-S cathode into a non-water-soluble PEDOT cathode to obtain a non-water-soluble PEDOT solid capacitor.

[0059] Combination Figure 1 and Figure 2 As shown in Figure 2, by analyzing the sulfur spectrum of the cathode film dried at 120°C and 180°C using X-ray photoelectron spectroscopy (XPS), it was found that at 120°C, the ratio of S in the sulfonate group to S in the thiophene was 1:1, indicating that the side chain was not broken and the material still existed in the form of water-soluble PEDOT-S; when the temperature was raised to 180°C, the ratio of S in the sulfonate group to S in the thiophene dropped to 0.62:1, indicating that some side chains were broken (see the mechanism diagram). Figure 3 As shown in Table 1, the water-soluble PEDOT-S is converted into the water-insoluble PEDOT through temperature control, thereby maintaining the stable performance of the capacitor and avoiding the problem of water absorption of the capacitor during long-term storage.

[0060] Table 1 Comparison of material properties at different drying temperatures

[0061]

[0062] It should be noted that the water-soluble PEDOT-S is formed into a water-soluble PEDOT-S cathode in the capacitor through an impregnation process, and then dried at a temperature of 150 to 180°C to form a water-insoluble PEDOT cathode, thereby obtaining a water-insoluble PEDOT solid capacitor. After testing, the water-insoluble PEDOT solid capacitor exhibits high extraction capacitance (CAP), low leakage current (Lc), and low ESR. Its comprehensive performance is better than that of the capacitor using traditional PEDOT:PSS, and it solves the problems of large particle size, stratification, and the need to add dopants to improve conductivity in traditional PEDOT:PSS. Since the water-soluble PEDOT-S is converted into water-insoluble PEDOT, not only the performance of the capacitor is more stable, but also the problem of water absorption of the capacitor during long-term storage is avoided.

[0063] It should be noted that, in this article, the terms "include", "comprises" or any other variations thereof are intended to cover non-exclusive inclusion, so that a process, method, article or device including a series of elements includes not only those elements, but also other elements not explicitly listed, or also includes elements inherent to such process, method, article or device. In the absence of further restrictions, an element defined by the sentence "comprises a ..." does not exclude the existence of other identical elements in the process, method, article or device including the element.

[0064] In addition, it should be noted that the scope of the methods and applications in capacitors in the embodiments of the present invention is not limited to performing functions in the order shown or discussed, and may also include performing functions in a substantially simultaneous manner or in reverse order according to the functions involved, for example, the described methods may be performed in an order different from that described, and various steps may be added, omitted, or combined. In addition, features described with reference to certain examples may be combined in other examples.

[0065] The embodiments of the present invention are described above, but the present invention is not limited to the above-mentioned specific implementation modes. The above-mentioned specific implementation modes are merely illustrative and not restrictive. Under the guidance of the present invention, ordinary technicians in this field can also make many forms without departing from the scope of protection of the purpose of the present invention and the claims, all of which are protected by the present invention.

Claims

1. A method for preparing water-soluble PEDOT-S, characterized in that: The steps include: Step S1, providing a water-soluble EDOT monomer; Step S2, dissolving the water-soluble EDOT monomer in deionized water, adding a catalyst, and stirring evenly to obtain a mixed solution; Step S3, under a nitrogen protection environment, adding an oxidant solution dropwise to the mixed solution for reaction, and obtaining an intermediate product after the reaction is completed; Step S4, treating the intermediate product with a dialysis membrane or an ion exchange resin to remove low molecular weight byproducts, thereby obtaining a water-soluble PEDOT-S solution with high dispersibility and low viscosity.

2. The method for preparing water-soluble PEDOT-S according to claim 1, characterized in that: In step S1, the preparation method of the water-soluble EDOT monomer is as follows: Hydroxymethyl EDOT is dissolved in an appropriate amount of deionized water, sodium hydride is added, and a sulfonic acid reagent or a carboxylation reagent is added dropwise after stirring at room temperature for a certain period of time, and then the temperature is raised to reflux for a certain period of time, and a water-soluble EDOT monomer containing a sulfonic acid group or a carboxyl group is obtained after purification.

3. The method for preparing water-soluble PEDOT-S according to claim 2, characterized in that: The molar ratio of hydroxymethyl EDOT to sodium hydride is 1:1.0-1.

5.

4. The method for preparing water-soluble PEDOT-S according to claim 2, characterized in that: The mixture was stirred at room temperature for 4 hours and then refluxed for 15 to 24 hours.

5. The method for preparing water-soluble PEDOT-S according to claim 1, characterized in that: In step S2, the molar ratio of the catalyst to the water-soluble EDOT monomer is 0.2 to 1:

1.

6. The method for preparing water-soluble PEDOT-S according to claim 5, characterized in that: In step S2, the catalyst is ferrous sulfate or ferric sulfate.

7. The method for preparing water-soluble PEDOT-S according to claim 5, characterized in that: In step S3 , the molar ratio of the oxidant to the water-soluble EDOT monomer is 1 to 2:

1.

8. The method for preparing water-soluble PEDOT-S according to claim 7, characterized in that: In step S3, the oxidant is sodium persulfate or ammonium persulfate.

9. The method for preparing water-soluble PEDOT-S according to claim 1, characterized in that: In step S3, the dropping time is no longer than 30 minutes, and the reaction temperature is 25°C.

10. Use of the water-soluble PEDOT-S prepared by the preparation method according to any one of claims 1 to 9 in the preparation of water-insoluble PEDOT solid capacitors, characterized in that: include: The capacitor is immersed in a water-soluble PEDOT-S solution to obtain a capacitor with a water-soluble PEDOT-S cathode after sufficient infiltration. The capacitor is dried at a temperature of 150 to 180° C. to convert the water-soluble PEDOT-S cathode into a non-water-soluble PEDOT cathode to obtain a non-water-soluble PEDOT solid capacitor.

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